.Net COM object in C++ Builder

I'm new to C++ Builder and I'm trying to use an existing .Net VB DLL (non
visual), exported as a COM object, within a Win32 C++ app. 

I've created a test project and 'imported' the component, which then created the
.cpp and .h files for the .dll (TestInterop_TLB) and mscorlib_TLB, which I have
included in my project. 

The problem comes when I compile the app I get 51 errors referring to problems
with mscorlib_TLB.h:
[BCC32 Error] mscorlib_TLB.h(8901): E2090 Qualifier 'System' is not a class or
namespace name

Does anyone know what this error is referring to and how to overcome it...?